This invention relates to a balloon catheter with a shaft having at its distal end a balloon. The shaft has one lumen through which the balloon is supplied and another lumen through which a guide wire is passed. The guide wire functions to guide and control the catheter in use. The shaft consists of a proximal area and a distal area, with the shaft being made of a stiffer material in the proximal area. The lumen for the guide wire is coaxially located in the proximal area of the shaft so that the lumen for supplying the balloon surrounds the lumen for the guide wire like a ring. In the distal area the shaft is made of a more flexible material and the lumen for supplying the balloon and the lumen for the guide wire are arranged biaxially side by side.
A balloon catheter of this type is disclosed, for example, in German Utility Patent 9,106,499. The balloon catheter disclosed there is used together with a guide catheter and a guide wire for percutaneous transluminal coronary recanalization. The catheter is inserted into a blood vessel through a puncture in the skin and is advanced through the blood vessel to an arteriosclerotic occlusion in coronary vessels, for example. Then the occlusion is widened with the inflatable balloon at the end of the catheter.
The shaft of this known catheter is composed of two lengths. The proximal length on the operating end is made of an especially rigid material and is also arranged coaxially, i.e., according to the "tube-in-a-tube" system, which leads to an especially rigid shaft in this area.
The distal length of the shaft on the end remote from the manipulator is made of an especially flexible material and is designed so the two lumens in the shaft, namely the channel for supplying the balloon and the channel for receiving the guide 7ire, are arranged side by side in a joint shaft sheathing. This yields a more flexible design, so the two measures together, namely the flexible material and the more flexible design, yield a shaft that can adapt to all blood vessel shapes.
This arrangement should achieve the effect that, on the one hand, the distal end of the catheter with the balloon folded up can be inserted easily into the convoluted passages of the coronary vessels but, on the other hand, the shearing forces for advancing the catheter can be transmitted well in the proximal rigid section of the shaft at the same time.
If the proximal section is not rigid enough, the shaft will give to the side under the shearing forces as the catheter is advanced, and especially high frictional forces will develop between the catheter and the side wall in the areas where the catheter yields to the side. Some of the shearing force applied to the shaft is thus lost and is no longer available for pushing through a vascular occlusion, for example. This also means that some of the sensory perception is lost for the treating physician since some of the resistance perceived by the physician in advancing the catheter is due to uncontrolled frictional forces rather than resistance that should be taken into account by the physician in performing the treatment. This lateral yielding of the catheter shaft in advancing the catheter also means that the tip of the catheter, the balloon, does not cover the same distance as the proximal end. The safety and reliability with which the doctor can guide the catheter are then greatly impaired.
It is desirable that a catheter of this type can also be used according to the so-called monorail system. With this system which is described in European Patent 203,945, the guide wire which is guided from the tip inside the catheter does not come out of the shaft at the proximal end of the catheter but instead comes out of the shaft at a certain short distance from the balloon. This facilitates changing catheters while the guide wire is in the blood vessel with its end after the occlusion. Without this outlet opening a short distance from the balloon, i.e., without the monorail system, the guide wire would have to project out of the patient's body for a length at least equal to the total catheter length. With the monorail system the guide wire can be much shorter and changing catheters is easier and faster accordingly. Less effort in manipulation is required to keep the guide wire that projects out of the patient's body sterile, and the catheter need not be advanced over a guide wire approximately 3 meters long, for example.